The present invention relates to a developing method and a developing apparatus, and more particularly, to a method and developing apparatus for performing a developing process by applying developing solution to a surface of a substrate such as a semiconductor wafer.
To manufacture a semiconductor device, photolithography technique is used. In the photolithography technique, photoresist is coated on a semiconductor wafer, thereby forming a photoresist film on one surface of the wafer. The photoresist film is exposed to a predetermined circuit pattern and then developed. Thus, a predetermined pattern photoresist film is formed on the wafer.
In general, the wafer is developed in the following manner. First, the developing solution is continuously applied from a nozzle to the photoresist film to which the circuit pattern has been exposed. The applied developing solution forms a layer, which contacts that surface of the photoresist film. The layer of developing solution is maintained on the resist film for a prescribed time, by continuously applying the developing solution.
Recently, a linear nozzle 100 of the type shown in FIG. 7 is used to apply developing solution in order to save the developing solution and to apply a developing solution uniformaly over an entire surface of the wafer. The linear nozzle 100 has a number of discharge holes 101 arranged in a straight line. To develop the resist film formed on a wafer 102, the nozzle 100 is moved to face the wafer 102. The nozzle 100 applies the developing solution through the holes 101 onto the wafer 102, in the form of parallel streams. When the streams of developing solution merge on the surface of the resist film to form a film-like stream, then, the wafer 102 is slowly rotated by 180xc2x0. After the developing solution layer covers the entire surface of the resist film, the rotation speed of the wafer 102 is increased.
The conventional method of developing the resist film by the use of the linear nozzle 100 is, however, disadvantageous in the following respects:
(1) It takes some time until the developing solution 103 spreads all over the pattern-forming surface of the wafer 102. This is because the wafer 102 is rotated only after the developing solution 103 is applied onto the resist film. Consequently, that part of the resist film, which first contacts the developing solution 103 may differ from any other part of the resist film in terms of resolution.
To be more specific, the parallel streams of developing solution 103 applied through the holes 101 merge together on the resist film, forming a film-like stream. The wafer 100 must be rotated only after the developing solution forms a film-like stream. It is therefore impossible to rotate the wafer 102 before or at the same time the developing solution 103 first contacts the photoresist film. As a consequence, that part of the resist film, which first contacts the solution 103, may be developed to excess, unlike any other part of the resist film.
(2) Second, much attention must be now pad to the influence of the first impact given by the developing solution 103 that first contacts the resist film.
That is, when the valve connected to the linear nozzle 100 is opened to supply the developing solution 103 to the nozzle 100, the pressure on the solution 103 increases momentarily. Thus, the streams of developing solution applied from the nozzle 100 give the first impact to the wafer 102. Consequently, that part of the resist film, which first contacts the solution 103, is developed to excess, unlike any other part of the resist film.
The circuit patterns recently designed and formed on the wafer consist of very fine elements arranged in high density, and the resist film must be processed with high resolution. This is why the influence of the first impact, which has hitherto been neglected, now needs to be considered.
As described above, the conventional developing method is disadvantageous in view of the non-uniform development of the resist film, which results not only from the different timings of applying the developing solution to the resist film, but also from the influence of the first impact of developing solution.
The present invention has been made in view of the foregoing. Its object is to provide a developing method and a developing apparatus, which solves various problems arising in applying a developing solution on a wafer, thereby to properly develop the photoresist film formed on the wafer.
More particularly, the object of the invention is to provide a developing method and a developing apparatus, in which no time lag in the application of developing solution for the parts of the resist film takes place, making it possible to develop the photoresist film uniformly.
Another object of the invention is to provide a developing method and a developing apparatus, which prevent the first impact of the developing solution on the photoresist film from impairing the developing of the photoresist film.
To attain the objects of the invention, a developing method according to the first aspect of the invention comprises the steps of: holding a substrate in a substantially horizontal position, the substrate coated with a photoresist film which has a pattern-exposed region where a circuit pattern is formed by light exposure; and developing the photoresist film by applying, at a time, a developing solution to the entire pattern-exposed region of the photoresist film.
In the cross-sectional area of the photoresist film, which can be applied with the developing solution at a time, is larger than in the conventional method in which the solution is applied by the linear nozzle. The developing solution can be therefore applied at a lower speed to the pattern-forming region of the resist film. Hence, it is possible to reduce the influence that the first impact of solution imposes on the resist film.
The developing solution may be is applied to the resist film, in the form of parallel streams. However, the streams of solution merge on the resist film, forming a layer of solution thereon more quickly than in the conventional method. Therefore, the substrate can be rotated before the start of applying the developing solution to the photoresist film, and at a higher speed than in the conventional developing method. Moreover, this effectively reduces the influence of the first impact of developing solution.
With the developing method of the invention it is possible to apply the developing solution, almost at a time, to the entire pattern-exposed region of the resist film. Thus, no time lag in the application of solution for the parts of the resist film takes place. This makes it possible to develop the resist film uniformly. As a result, the resist film can have uniform resolution over its entire pattern-exposed region.
In the developing method of the invention, if the developing solution is applied at a higher rate, the developing solution can be uniformaly applied over the entire photoresist film without rotating the substrate.
According to the second aspect of the present invention, there is provided a developing apparatus which comprises: a substrate holding mechanism for holding a substrate in a substantially horizontal position, the substrate coated by a photoresist film which has a pattern-exposed region where a circuit pattern is formed by light exposure; a solution discharging unit having a number of discharge tubes, each having a distal end opposing the pattern-exposed region of the photoresist film; a solution applying mechanism for applying the developing solution to the pattern-exposed region of the photoresist film through the discharge tubes; and a control section for controlling the solution applying mechanism, thereby to apply the developing solution to the entire pattern-exposed region substantially at a same time.
Comprising these components, the developing apparatus can perform the developing method according to the first aspect of the invention. The apparatus may be designed such that the developing solution is applied through some of the discharge tubes to develop the resist film formed on a small wafer, and through all discharge tubes to develop the resist film formed on a large wafer.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.